From adacc5283eb660501b8c43ca8363bf9e0dfce051 Mon Sep 17 00:00:00 2001
From: Bastian Blokland <bastianblokland@gmail.com>
Date: Wed, 8 Jan 2020 23:36:17 +0200
Subject: [PATCH] Add '??' overloadable operator

---
 include/lex/token_kind.hpp          | 1 +
 include/prog/operator.hpp           | 1 +
 src/frontend/internal/utilities.cpp | 4 ++++
 src/lex/lexer.cpp                   | 4 ++++
 src/lex/token_cat.cpp               | 1 +
 src/lex/token_kind.cpp              | 3 +++
 src/parse/op_precedence.cpp         | 1 +
 src/prog/operator.cpp               | 2 ++
 tests/lex/operators_test.cpp        | 1 +
 9 files changed, 18 insertions(+)

diff --git a/include/lex/token_kind.hpp b/include/lex/token_kind.hpp
index 697028c8..5509d4a7 100644
--- a/include/lex/token_kind.hpp
+++ b/include/lex/token_kind.hpp
@@ -27,6 +27,7 @@ enum class TokenKind {
   OpGtEq,
   OpSemi,
   OpQMark,
+  OpQMarkQMark,
   OpDot,
   OpColonColon,
   OpSquareSquare,
diff --git a/include/prog/operator.hpp b/include/prog/operator.hpp
index 3e7118fd..15f0965c 100644
--- a/include/prog/operator.hpp
+++ b/include/prog/operator.hpp
@@ -24,6 +24,7 @@ enum class Operator {
   ColonColon,
   SquareSquare,
   ParenParen,
+  QMarkQMark,
 };
 
 auto getFuncName(Operator op) -> std::string;
diff --git a/src/frontend/internal/utilities.cpp b/src/frontend/internal/utilities.cpp
index 76a33303..b9e7385c 100644
--- a/src/frontend/internal/utilities.cpp
+++ b/src/frontend/internal/utilities.cpp
@@ -91,6 +91,8 @@ auto getOperator(const lex::Token& token) -> std::optional<prog::Operator> {
     return prog::Operator::SquareSquare;
   case lex::TokenKind::OpParenParen:
     return prog::Operator::ParenParen;
+  case lex::TokenKind::OpQMarkQMark:
+    return prog::Operator::QMarkQMark;
   default:
     return std::nullopt;
   }
@@ -138,6 +140,8 @@ auto getText(const prog::Operator& op) -> std::string {
     return "[]";
   case prog::Operator::ParenParen:
     return "()";
+  case prog::Operator::QMarkQMark:
+    return "??";
   }
   return "__unknown";
 }
diff --git a/src/lex/lexer.cpp b/src/lex/lexer.cpp
index 3f27af3f..d6faabb1 100644
--- a/src/lex/lexer.cpp
+++ b/src/lex/lexer.cpp
@@ -139,6 +139,10 @@ auto LexerImpl::next() -> Token {
     case ';':
       return basicToken(TokenKind::OpSemi, input::Span{m_inputPos});
     case '?':
+      if (peekChar(0) == '?') {
+        consumeChar();
+        return basicToken(TokenKind::OpQMarkQMark, input::Span{m_inputPos - 1, m_inputPos});
+      }
       return basicToken(TokenKind::OpQMark, input::Span{m_inputPos});
     case '.':
       if (isDigit(peekChar(0))) {
diff --git a/src/lex/token_cat.cpp b/src/lex/token_cat.cpp
index 7b012821..7b6bcab8 100644
--- a/src/lex/token_cat.cpp
+++ b/src/lex/token_cat.cpp
@@ -56,6 +56,7 @@ auto lookupCat(const TokenKind kind) -> TokenCat {
   case TokenKind::OpGtEq:
   case TokenKind::OpSemi:
   case TokenKind::OpQMark:
+  case TokenKind::OpQMarkQMark:
   case TokenKind::OpDot:
   case TokenKind::OpColonColon:
   case TokenKind::OpSquareSquare:
diff --git a/src/lex/token_kind.cpp b/src/lex/token_kind.cpp
index ee73719a..dae638e4 100644
--- a/src/lex/token_kind.cpp
+++ b/src/lex/token_kind.cpp
@@ -70,6 +70,9 @@ auto operator<<(std::ostream& out, const TokenKind& rhs) -> std::ostream& {
   case TokenKind::OpQMark:
     out << "qmark";
     break;
+  case TokenKind::OpQMarkQMark:
+    out << "qmarkqmark";
+    break;
   case TokenKind::OpDot:
     out << "dot";
     break;
diff --git a/src/parse/op_precedence.cpp b/src/parse/op_precedence.cpp
index 84f7b906..a70d934a 100644
--- a/src/parse/op_precedence.cpp
+++ b/src/parse/op_precedence.cpp
@@ -19,6 +19,7 @@ auto getRhsOpPrecedence(const lex::Token& token) -> int {
   case lex::TokenKind::OpParenParen:
   case lex::TokenKind::SepOpenParen:
   case lex::TokenKind::SepOpenSquare:
+  case lex::TokenKind::OpQMarkQMark:
   case lex::TokenKind::OpDot:
     return callPrecedence;
   case lex::TokenKind::OpStar:
diff --git a/src/prog/operator.cpp b/src/prog/operator.cpp
index d33f75c9..b0b7b998 100644
--- a/src/prog/operator.cpp
+++ b/src/prog/operator.cpp
@@ -45,6 +45,8 @@ auto getFuncName(Operator op) -> std::string {
     return "__op_squaresquare";
   case Operator::ParenParen:
     return "__op_parenparen";
+  case Operator::QMarkQMark:
+    return "__op_qmarkqmark";
   }
   throw std::invalid_argument("Unknown operator");
 }
diff --git a/tests/lex/operators_test.cpp b/tests/lex/operators_test.cpp
index 75aa6904..5231f59d 100644
--- a/tests/lex/operators_test.cpp
+++ b/tests/lex/operators_test.cpp
@@ -26,6 +26,7 @@ TEST_CASE("Lexing operators", "[lex]") {
   CHECK_TOKENS(">=", basicToken(TokenKind::OpGtEq));
   CHECK_TOKENS(";", basicToken(TokenKind::OpSemi));
   CHECK_TOKENS("?", basicToken(TokenKind::OpQMark));
+  CHECK_TOKENS("??", basicToken(TokenKind::OpQMarkQMark));
   CHECK_TOKENS(".", basicToken(TokenKind::OpDot));
   CHECK_TOKENS("::", basicToken(TokenKind::OpColonColon));
   CHECK_TOKENS("[]", basicToken(TokenKind::OpSquareSquare));